Senior Full Stack Software Engineer at Mercor

Senior Full Stack Engineer | $90–110/hr | Remote (US)

Join a leading AI lab's GenAI team and play a central role in building foundational AI models from the ground up. As a Senior Full Stack Software Engineer, you'll build, integrate, and stress-test real software on top of frontier models — working directly with the AI lab's engineering manager on fast-moving, high-impact projects. This is a full-time W-2 position (40 hrs/week) employed through Cincinnatus LLC.

Key Responsibilities

• Build and ship full-stack applications, services, and internal tools in Python, Java, Rust, C#, C++, or TypeScript that exercise frontier model capabilities end to end.
• Integrate pre-release model APIs into working software, including tool interfaces, evaluation harnesses, and telemetry scaffolding.
• Diagnose and document model and integration failure modes, translating engineering observations into clear written feedback for research teams.
• Prototype rapidly against shifting requirements, delivering working increments with minimal up-front specification.
• Collaborate with the engineering manager and peers to maintain code quality, architecture consistency, and technical documentation.

Core Qualifications

• 6+ years of professional experience building and shipping production software at a recognized, top-tier organization, with end-to-end system ownership.
• Deep production expertise in at least one of Python, Java, Rust, C#, or C++, plus demonstrated delivery in a second language from a different ecosystem.
• Hands-on full-stack ownership: backend services and API design, a modern front-end framework (React or equivalent), data modeling, and cloud deployment.
• Proven ability to onboard onto unfamiliar codebases and deliver working code quickly with minimal ramp-up time.
• Demonstrable career progression and strong written communication skills.
• Availability for at least 40 hours/week during weekdays.

Cincinnatus LLC is an Equal Employment Opportunity employer. We welcome applicants of all backgrounds and do not discriminate on the basis of race, gender, age, disability, veteran status, or any other protected characteristic.